1. Field of the Invention
The present invention relates to a diaphragm mechanism and a shutter mechanism for a camera, and more particularly to a diaphragm device and a shutter device for an electronic camera, such as a digital video camera and a digital still camera, which photographs an object by converting an optical image of an object into electric signals using a solid photographing element including a charge coupled device (CCD) or the like.
2. Discussion of the Background
In a video camera for photographing a dynamic image, generally a solid photographing element such as a solid photographing element including a charge coupled device (CCD) is used as a photographing light receiving element. Furthermore in recent years, digital still cameras have come in widespread use. Such digital still cameras photograph an object image by using a solid photographing element to obtain image data of a still image of the object and record it digitally into an integrated circuit (IC) card or a floppy disk. Among these digital cameras, some are capable of photographing not only a still image but also a dynamic image (a movie image).
As methods of reading out photoelectric-converted pixels in a solid photographing element such as, for example, a CCD solid photographing element, there are a field read-out method and a frame read-out method. For photographing a still image, there are increasing cases of using the frame read-out method which is advantageous in resolution and the like.
In the frame read-out method, an odd number of field transfer read-out operations and an even number of field transfer read-out operations must be performed sequentially. Further, physical light shielding is generally required to the CCD solid photographing element immediately after completion of an appropriate exposure in order to prevent a defective phenomenon such as a smear caused by an exposure during the read-out operation.
In a CCD solid photographing element of a total pixel read-out type, the light shielding after the exposure as described above is not required. However, the above total pixel read-out type CCD solid photographing element is hard to enhance in the number of pixels for manufacturing reasons. Therefore, from the viewpoint of difficulties in manufacturing, an interlace-type CCD solid photographing element is still advantageous though it requires physical light shielding.
The following is general process of photographing a still image with an electronic camera having an electronic finder with a monitor display of a liquid crystal display (LCD) and a zoom lens in which light shielding is performed after completion of an exposure in the frame read-out method.
(1) Turn on the camera.
(2) Set the camera to a photographing (i.e., recording) mode.
(3) Measure luminance of an outside world, particularly that of a field of photographing. Then, a diaphragm is automatically set according to the measured value.
(4) A through image captured by the CCD solid photographing element is displayed, for example on an LCD monitor screen.
(5) Set a zoom position, if necessary.
(6)Determine the composition and depress a release button.
(7) An auto-focus (AF) mechanism is actuated and the photographing lens is moved to a focal position.
(8) An exposure for the CCD solid photographing element is commenced.
(9) The CCD solid photographing element is shielded from the exposure light after an appropriate time period.
(10) The CCD solid photographing element reads out data by an odd number field transfer and by an even number field transfer.
(11) A signal processing device performs display, recording, or other processing appropriately onto image information read out from the CCD solid photographing element.
(12) Start the next photographing operation, or stop the photographing and turn off the camera.
When using a single-focus lens or a fixed-focus lens instead of the zoom lens or in photographing with an electric flash, a process partially different from the above is applied. In every case, however, two different operations, diaphragm setting and light shielding, are required in the photographing process as above, and various improvements have been attempted.
For example, Japanese Patent Publication No. 2622296 discloses accomplishing a diaphragm function and a light shielding function by providing a plurality of diaphragm apertures and a shielding portion adjacent to each of the diaphragm apertures.
Additionally, Japanese Unexamined Patent Publication No. 7-11616 discloses accomplishing a diaphragm function and a light shielding function in almost the same manner as the above Japanese Patent Publication No. 2622296 by providing a turret-type diaphragm sheet having a plurality of diagram apertures and a shielding sheet having a double-sheet configuration arranged separately from the diaphragm sheet with the diaphragm sheet and shielding sheet coupled with each other.
As described above, generally, two separate types of operations, diaphragm setting 5 and light shielding, have been required in a still image photographing process, and therefore, as disclosed in the Japanese Patent Publication No. 2622296 and Japanese Unexamined Patent Publication No. 7-11616, the diaphragm function and the light shielding function are achieved by providing diaphragm apertures and shielding members, each operated independently.
In the Japanese Patent Publication No. 2622296, however, because the exposure and light shielding operations are performed by simply sliding a diaphragm sheet having a plurality of diaphragm apertures, there is a problem that light shielding is performed by a shift of a diaphragm aperture itself having a diaphragm aperture size selected during an exposure. In other words, the exposure operation is generally continued until the diaphragm aperture selected during the exposure is covered behind any end portion of a peripheral portion of an opened diaphragm aperture of the optical system, and therefore an irregular exposure occurs on a surface of the image obtained. In addition, when a moving object is photographed, an unfavorable phenomenon may occur, such as a blurred image, or a deformed object image depending upon a moving direction of the diaphragm aperture and that of the object for photographing even if the camera has a shutter speed (an exposure time between a commencement of the exposure and completion of the light shielding) at which an image can be captured normally.
In addition, because the shielding operation is started from an end of the diaphragm aperture, particularly when a large aperture size is selected, time is consumed from a commencement of light shielding to a completion thereof, which causes the same results as caused by a low shutter speed and a long exposure time, thus causing a problem that blurring easily occurs from an unsteady hold on the camera.
Furthermore, in the Japanese Unexamined Patent Publication No. 7-11616, a shielding sheet having a double-sheet configuration is arranged separately from the turret-type diaphragm sheet. As a result, it is further needed to arrange a coupling member and an energizing spring for opening or closing the shielding sheet, by which the mechanism is complicated.
Still further, because there is no arrangement of a positioning device on the shielding sheet, when the diaphragm aperture is positioned with a stepping motor, due to a step position precision of the stepping motor itself or the like, a diaphragm aperture cannot be set in an accurate position.
Furthermore, when a desired diaphragm aperture size is selected with a turret-type diaphragm sheet, diaphragm apertures having other diaphragm aperture sizes pass the opened diaphragm aperture of the optical system. Therefore, there is a problem that the shielding sheet is opened and closed on all such occasions wastefully, which causes a deterioration of durability of the mechanism or some failure and also generates uncomfortable mechanical sounds when the mechanism is operated.
More recently, there are various improved constitutions in which the shutter is operated after the diaphragm aperture is set by a single motor. However, in such constitutions, because a series of operations is generally treated as a single sequence, it is hard to arbitrarily change the diaphragm aperture after the diaphragm aperture has been once set. Therefore, these constitutions have a tendency to have a disadvantage such as a need for re-executing the sequence from the beginning to change the diaphragm aperture or involving an unnecessary shutter operation.
The present invention has been made in view of the above-discussed and other problems and addresses the above-discussed and other problems.
Preferred embodiments of the present invention provide a novel diaphragm device in which a reliable diaphragm performance and a high diaphragm precision are achieved and respective functions are performed independently from each other and stably.
Preferred embodiments further provide a novel diaphragm device in which a diaphragm sheet can be small in its external size so as to achieve downsizing of the entire camera and reliable positioning of the diaphragm sheet can be achieved in a simple constitution.
Further, preferred embodiments provide a novel diaphragm device in which a positioning member for positioning a diaphragm sheet is integrated with a position detecting member for detecting a position of the diaphragm sheet so as to detect the position reliably without error in a simple constitution and in which a specific diaphragm aperture position can be detected reliably, very precisely, and durably.
Furthermore, preferred embodiments provide a novel diaphragm device in which a diaphragm sheet can be set reliably in a predetermined position.
Preferred embodiments of the present invention provide a novel shutter device in which an identical rotary ring can be used to control opening or closing of a shutter independently of diaphragm aperture setting and thereby multi-functions, space saving, and low cost are achieved with a small number of members.
Preferred embodiments further provide a novel shutter device in which a high-precision control of the shutter device can be achieved in relation with a diaphragm setting.
Preferred embodiments further provide a novel shutter device in which a series of opening and closing operations of the shutter device can be performed simply with forward and reverse rotation of a rotary ring without a need for a fastening release actuator and the like and which is therefore superior in cost, space, and reliability.
Further, preferred embodiments provide a novel shutter device in which there is no interference between the shutter open-close operation and the diaphragm aperture setting operation and each operation can be adjusted independently.
Furthermore, preferred embodiments provide a novel shutter device that allows photographing repeatedly at a high speed, and that thereby extends the photographing functions.
Furthermore, preferred embodiments provide a novel shutter device in which a light volume is adjustable at monitoring and a degree of freedom is high in a program diagram so as to reduce smear or other defects at high luminance which have been frequently found in background art.
Preferred embodiments further provide a novel shutter device in which regular shutter operations are achieved by reducing contact friction between shutter blades moving in opposite directions and in which a variable diaphragm aperture is achieved with a high exposure precision.
According to a preferred embodiment of the present invention, a digital camera has an optical image input system including a photographing element for converting an optical image input by an optical system to electric signals, a signal processor for applying predetermined signal processing to the electric signals obtained by the photographing element, and a diaphragm device adjusting an exposure time by controlling incident luminous flux to the photographing element and an electric charge storage time of the photographing element. According to the present invention, a novel diaphragm device includes a diaphragm sheet rotatably arranged around a rotation central shaft thereof which is set in parallel with a photographing optical axis of the optical system. The diaphragm sheet has a plurality of diaphragm apertures having different diameters arranged in a turret shape on a reference circle around the rotation central shaft having a radius equal to a distance from the rotation central shaft to the photographing optical axis. The diaphragm device includes a rotary ring arranged rotatably in forward and reverse directions around the photographing optical axis and a click member is retained by the rotary ring rotatably only in one direction so as to rotate the diaphragm sheet in one direction. A rotation driving device drives the rotary ring to rotate, and a positioning mechanism fastens the diaphragm sheet in a position setting a selected diaphragm aperture.
According to the present invention, rotation of the click member in a first direction is regulated by the rotary ring so that a tip of the click member is engaged with a protruding portion of the diaphragm sheet at rotation of the rotary ring in a predetermined direction, and the click member rotates in a second direction different from the first rotation direction while leaving the diaphragm sheet behind in the selected diaphragm aperture setting position at rotation of the rotary ring in a direction reverse to the predetermined direction after completion of setting the selected diaphragm aperture.
According to the present invention, the positioning mechanism may include recess portions formed on an outer periphery of the diaphragm sheet correspondingly to the diaphragm apertures, respectively, and a positioning member energized substantially toward the center of the diaphragm sheet and pushing the recess portion corresponding to the selected diaphragm aperture so that the diaphragm sheet is fastened and positioned in the selected diaphragm aperture setting position.
Further, the positioning member may include a positioning lever rotatable around the rotation central shaft set in parallel with the photographing optical axis. The positioning lever has a first protruding portion having a boss for fastening the diaphragm sheet and extending in a radial direction from a rotation axis of the positioning lever and a second protruding portion extending in a different radial direction for detecting a position of the diaphragm sheet.
According to the present invention, one of the recess portions may have a different shape from those of the other recess portions such that a rotation angle of the positioning lever when the boss of the positioning lever is engaged with the recess portion having the different shape is discriminated from rotation angles of the positioning lever when the boss of the positioning lever is engaged with the other recess portions. As a result, the diaphragm sheet is detected to be in a reference position setting one of the plurality of diaphragm apertures by a moving amount of the second protruding portion of the positioning lever for position detection. An optical sensor may be used for detecting the diaphragm sheet to be in the reference position with the second protruding portion of the positioning lever.
According to the present invention, each of the recess portions of the outer periphery of the diaphragm sheet may have a form such that the boss of the positioning lever drops from an outmost periphery of the diaphragm sheet toward a center thereof immediately before an arbitrary diaphragm aperture reaches the selected diaphragm aperture setting position and prevents rotation of the diaphragm sheet in a direction reverse to the predetermined rotation direction of the diaphragm sheet. Further, each part of the recess portions closest to the center of the diaphragm sheet may be formed so as to be symmetrical about a straight line connecting the center of the diaphragm sheet and that of the boss and to extend in a substantially radial direction from the center of the diaphragm sheet in order to balance a spring force of the boss toward the center of the diaphragm sheet.
Another preferred embodiment of the present invention provides a novel shutter device for a digital camera having an optical image input system including a photographing element for converting an optical image input by an optical system to electric signals and a signal processor for applying predetermined signal processing to the electric signals obtained by the photographing element. The shutter device has a diaphragm function of adjusting an exposure time by controlling incident luminous flux to the photographing element and an electric charge storage time of the photographing element and includes a diaphragm sheet rotatably arranged around a rotation central shaft set in parallel with a photographing optical axis of the optical system. The diaphragm sheet has a plurality of diaphragm apertures having different diameters arranged in a turret shape on a reference circle around the rotation central shaft having a radius equal to a distance from the rotation central shaft to the photographing optical axis. A rotary ring arranged rotatably in forward and reverse directions around the photographing optical axis includes a click member retained by the rotary ring rotatably only in one direction so as to rotate the diaphragm sheet in the one direction. A rotation driving device drives the rotary ring to rotate and a positioning mechanism fastens the diaphragm sheet in a position setting a selected diaphragm aperture. In addition, a shutter mechanism has a shutter blade for light shielding, and the light shielding shutter blade in a closed state is put in a release state in the middle of rotation of the rotary ring from an initial position of the rotary ring in a diaphragm aperture setting direction and, after completion of a diaphragm aperture setting, the light shielding shutter blade is closed in the middle of rotation of the rotary ring in a reverse direction for returning to the initial position.
According to the present invention, the rotary ring may have a member retaining the click member and a member controlling a releasing and closing operation of the shutter blade of the shutter mechanism, which are integrated with the rotary ring, respectively.
Further, the shutter mechanism may have an open-close lever energized so as to drive the shutter blade in a closing direction and a fastening lever energized to fasten the open-close lever in a released state, and a series of operations including pushing the open-close lever with the rotary ring, releasing the shutter blade, dropping the fastening lever, separating the rotary ring from the open-close lever, and fastening the open-close lever with the fastening lever are performed with rotation of the rotary ring from the initial position of the rotary ring. Another series of operations including kicking the fastening lever with the rotary ring, releasing the open-close lever fastened with the fastening lever, and closing the shutter blade by rotation of the open-close lever are performed with rotation of the rotary ring in a direction for returning to the initial position.
According to the present invention, the shutter blade may be released and closed by the shutter mechanism while the rotary ring rotates from the initial position to an intermediary rotated position before a maximally rotated position of the rotary ring and a selected diaphragm aperture may be set while the rotary ring rotates from the intermediary rotated position to the maximally rotated position, such that interference is not caused between operations of releasing and closing the shutter blade and setting the selected diaphragm aperture.
Furthermore, the rotary ring may be driven so as to repeatedly rotate from the initial position to the intermediary rotated position so that the shutter blade is repeatedly released and closed for repeatedly photographing at high speed.
Also, the rotary ring may be driven to rotate from the intermediary rotated position to the maximally rotated position so as to change the selected diaphragm aperture for adjusting a light volume at monitoring.
Further, the shutter mechanism may include two pieces of the shutter blade, and the two shutter blades may be arranged such that the diaphragm sheet is put between the two shutter blades in a direction of the photographing optical axis.